User Manual

36 8LS User’s Guide
Installation
A termination resistor is required at each end of the transmission line.
This is accomplished by applying a 200
Ω
resistor across the line at the
farthest point from the computer transmitter. Check with Watlow
Anafaze for setting the Black Box SW2 to the "term" position to
terminate the computer receive line.
The fifth wire for RS-485 communications is recommended for noisy
environment.
NOTE
Connect the cable shields to equipment ground
only at the 8LS controller sites. Do not connect the
shield at the computer site to Ground. Connect a
200 ohm terminating resistor between RX- and
RX+ at the 8LS.
For multiple units connect the system in parallel as follows:
RX
+ # 4
RX-
# 5
TX
+ # 2
TX
- # 3
200
RX
+ # 4
RX
- # 5
TX
+ # 2
TX
- # 3
TXA
TXB
RXA
RXB
8LS (n)
8LS (1
)
Black Box
LD485A
B&B Electronics
485OIS 485OIC
DB-25 Screws
Or
#2
#14
#5
#17
TDA
TDB
RDA
RDB
The "fifth" 12 VDC Com 12 VDC Com Logic COM Logic COM
wire